1. Field of the Invention
The present invention relates to an oil pump, and more particularly to oil pump for preventing misoperation of a regulator valve.
2. Background of the Related Art
A conventional oil pump 70 is disclosed in Japanese Utility Model Laid-open No. 62(1987)-67979, and is shown in FIG. 5. The oil pump 70 is used for an engine of a vehicle (not shown). In the oil pump 70, a pair of gears 71, 72 are located in a housing 79. An inlet port 74 is formed in the housing 79, and is connected to an inlet 73 which is formed in the housing 79. An outlet port 75 is formed in the housing 79, and the gears 71, 72 are located between the inlet port 74 and the outlet port 75. The outlet port 75 is connected to an outlet 78 and an inlet 76a of a regulator valve 76. An outlet 76b of the regulator valve 76 is connected to the inlet port 74 via a relief passage 77. A pair of shafts 80, 81 are snugly fitted with the gears 71, 72, and are supported by the housing 79.
In the above-mentioned oil pump 70, the oil which circulates in a hydraulic circuit (not shown) is led to the inlet port 74 via the inlet 73. The shaft 80 is driven by a crank shaft (not shown) of the engine, so that gears 71, 72 are rotated. Rotation of the gears 71, 72 perform a pumping function. Thus, the oil in the inlet port 74 is pumped to the outlet port 75.
The outlet 78 is located at right angles to the flow of oil discharged from the outlet port 75. Therefore, the oil discharged from the outlet port 75 flow directly into the inlet 76a of the regulator valve 76.
In general, the regulator valve 76 has as its function the keeping of the pressure of the oil pump 70 at a set value. But, the pumped oil flowing into the inlet 76a of the regulator valve 76 has both a dynamic pressure due to its flow velocity and a static pressure corresponding to the discharge pressure at the outlet 78. Therefore, the regulator valve 76 may operate to keep the discharge pressure at the outlet 78 at a low pressure because of the dynamic pressure effect on the regulator valve. This is a misoperation of the regulator valve of the oil pump.